Most of the time, in my (admittedly limited) experience. The two exceptions have been: A giant site, who already had an API & had deliberately decided to not

Most of the time, in my (admittedly limited) experience. The two exceptions have been: A giant site, who already had an API & had deliberately decided to not implement the API calls we wanted. I should add that another giant site have happily added API options for us. (For my client, really; not for me.) An archaic site. The dev team was gone & the owners were just letting it trickle them revenue until it died -- they didn't even want to think about it anymore.